Furthermore, while our theoretical and experimental results match very well for low and high frequencies, an evident discrepancy is observed before and after the cusp around the frequencies \(5.5\)  and \(7.5\)  Hz. We offer a heuristic support for this discrepancy by plotting the supremum of the resolvent norm (\( \sup _{f_r \in \mathbb {R}} ||\mathcal {R}||\) ), which indicates the maximum amplification over the excitation frequency \(f_r\)  [1]}:
\(\sup _{f_r \in \mathbb {R}} ||\mathcal {R}|| = \sup _{f_r \in \mathbb {R}} || (-i f_r B+ A)^{-1} ||,\) 
